Modulated pulse remote control



June 23, 1953 T. M. MANLEY ETAL l MODULATED PULSE REMOTE CONTROL Filed sept. 28 1945 June 23, 1953 T. M. MANLEY vEn AL MODULATED PULSE REMOTE CONTROL Filed Sept. 28, .1945

F/LITER REOE/VE'R 5 Sheets-Sheet 2 m/GGEH REcr/F/Ef? o/Rcu/r rR/GGER @Ear/HER c/Rcz//r rH/GGER y @Ear/HER c/Rcu/r rR/GGER RECT/F/ER CANCEL/NG c/Rcu/r RELAY CONTROL RELAY CONTROL RELAY OONTROI.

/fv VEN roR THEODORE M. MANLEY ROBERT R OHERPESK/ ATTORNEY 00N TOL RELAY cam/MOL 5 Sheets-Sheet 3 L A n v.. E L N A M M L MODULATED PULSE REMOTE CONTROL /VVE'NTOR THEORE M. MNLEY ROBERT F. l-/ERPESK/ 7" MMMQM.

ATTRNEV Filed Sept. 28, 1945 lune 23, 1953 T. M. MANLEY ETAL 2,643,369

MODULATED PULSE REMOTE CONTROL Filed Sep'.. 28, 1945 5 Sheets-Sheet 4 //V VE /V T01? THE'ODORE M. /WI/VLEY HUBERT E GHERPESK/ June 23, 1953 T. M. MANLEY ETAL 2,643,369

MODULATED PULSE REMOTE CONTROL Filed Sept. 28, 1945 5 Sheets-Sheet 5 CONTROL /N VEN TOI? THE ODO/7E M. MANLEY A TTORNE Y RELAY CON TROL RELAY ROBERT HERPESK/ TR/GGER G/RGU/ T GIRCU/ 7' REor/F/Ef? lama/fifa] REOTlF/ER FILTER FILTER Patented June 23, ..1953

2,643,369 MODULATED PULSE REMOTE CONTROL Theodore M. Manley, Xenia, and Robert P.

' Cherpeski, Dayton, Ohio Application September 28, 1945, SerialNo. 619,276

(Cl. S40-171) (Granted under Title 35, U. S. Gode .(1952), sec. 266) 8 Claims.

The invention described` herein may be manufactured and used by or for the Government for governmental purposes, withcut'the payment to us of any royalty thereon.

This invention relates to a system of remote control by radio signals and more particularly to means and method in a remote control radio system for initiating mechanical work.

In the past remote control radio systems have commonly been adapted for continuously maintaining a radio carrier upon which control signals have been impressed or applied when and as required.

Itis among the objects of the present invention to provide an improved remote control radio system that does not require the continuous maintenance of a radio carrier; that uses a control signal of very short time duration in the order of one-thousandth of one second which, in the absence of a continuous carrier, is difiicult of detection; and that uses a control signal which is adapted for transmission at suciently intense high power because of its brief duration so that it is detectable through radio interference of less power and with a minimum of overall energy output at the transmitter.

The above objects are augmented by additional objects that will be apparent to those who are in formed in the eld of remote control radio systems from the following description of an illustrative embodiment of the present inventionthat is presented in Vthe accompanying drawings; wherein:

Fig. 1 is a block and schematic diagram of a preferred transmitting system that embodies the' present invention;

Fig. 2 is a, block diagram of a preferred receiving system that embodies the present invention;

Fig. 3 is a block and schematic diagram of the receiving system that is shown in Fig. 2;

Fig. 4 is a fragmentary block and schematic diagram of a portion of the receiving system that is shown in Fig. 2;

Fig. 5 is a fragmentary diagram of a modification in the trigger cancelling portion of the circuit that is shown in Fig. 2; and

Fig. 6 is a block and schematic diagram of a modification of the receiving system that is shown in Fig. 2.

The remote .control radio system that is con-v templated hereby preferably uses a high frequency alternating-current carrier of, for example, 100 megacycles or over to which is applied modulation frequencies `oi the order, for example, of 1 megacycle or more. These modulation frequenciesmay be altered at will. The carrier is only transmitted when sending a control signal and then for a short time duration of one onethousandth of onev second or the like. The high frequency of the control signal modulation upon its carrier assists in its isolation in a lter at the receiver even though the time duration of the signal is very brief. The band width of the lter that is required to carry the signal modulation is not excessive due to the high frequency of the carrier upon which the signal modulation is impressed.

The receiver preferably is pretuned to the carrier and hence. the tuning of the receiver to the carrier frequency. is avoided. The time duration of vthe control signal is so short vthat it is not readily observed and the responsive control is actuated so quickly that it cannot readily be prevented. The application of known pulse technique at the transmitting equipment permits the use of sufliciently high power in the signal so that its power materially exceeds lany interfering continuous Wave form of transmission that could be maintained.

A preferred transmitting assembly that embodies a part of the present invention is illustrated in block and schematic diagram in Fig. 1 of the accompanyingv drawings. In the transmitting assembly a desiredv plurality of modulation oscillators I, 2, 3, 4, etc. separately apply their alternating current outputs through a corresponding number of electronic switches 5, B, l, 8, etc., and circuit conductors 9 and I0 to a transmitter Il. Signall from the transmitter Il is radiatedfrom a transmitting antenna I2.

The modulation oscillators l, 2, 3, 4, etc. have individually different rates of oscillation. The functioning ofV the electronic switches 5, E, 1, 8, etc. is controlled by the manual operation of corresponding switches 5', 6', l', 8', etc. respectively. For each closure of one of the switches 5', B', 'l'. 8', etc. the transmitter Il emits a single alternating current pulse of radio carrier of a denite predetermined short time duration, such as one one-thousandth of one second preferably, irrespective of `the time during which the switch 5', 6', 1', 8', etc. remains closed. The electronic switch as 5, 6, 1, 8, etc. are duplications of each other and hence a detailed description of the electronic switch 5 may be taken as being illustrative of the other electronic switches is held closed in the transmittingA circuit of the system.

The schematic diagram of the electronic switching of the modulating and transmitting system that is shown in Fig. l as exemplified by that in the electronic switch 5, comprises electron tubes and |26 that are connected to provide a usual one-shot multivibrator circuit. The tube |26 is normally conducting since its grid is returned to cathode through a resistor |21. Resistor |52 is the plate load resistance of tube |26. The tube |25 is cut off by the potential developed across the common cathode resistor |28 due to the conduction of the tube |26. The grid of tube |25 is returned to ground through a resistor |29. Closing of the switch 5 causes thefull positive potential of battery |30 to be applied instantaneously to the grid of the tube |25 across resistor |29. The potential decreases rapidly to zero as a capacitor is charged to the voltage of battery |30. The effect is to impress a very short positive pulse upon the grid of the tube |25' which causes tube |25 to start to conduct current. The resultant current ilow through the resistor |36 produces a change in potential across capacitor |31 which causes a negative potential to be impressed on the grid of the tube |26 across resistor |21, causing the tube |26 to stop conducting. The negative voltage on the grid of the tube |26 decreases as the capacitor |31 is discharged through the resistors |21, |28 and |36. When the negative potential across the resistor |21 reaches a value that is less than the cut-off bias of the tube |26, the tube |26 again begins to conduct and cuts off the conduction of the tube |25.

The time that tube |25 conducts after -the closure of the switch 5 may be adjusted by varying the time constant of the combination capacitor |31, and the resistors |21, |28 and |36. Preferably, the time constant is very short so that the time during which the tube 25 conducts is in the order of one one-thousandths of one second or one millisecond. A positive pulse of one millisecond duration is developed across resistor |46 each time the switch 5 is closed. The positive pulse can be used to key the output of any one of the modulation oscillators 2, 3, or 4, of which the modulation oscillator is taken as being representative, and to energize the transmitter through the circuit conductor 0. The direct current pulse voltage represented by the square wave |50 is coupled by a capacitor |5| to the grid of the tube |42 and along conductor i0 to the transmitter I as a keying pulse therefor. A battery |4| is connected in series with the resistor |46 which serves as grid return for a tube |42, so that the tube |42 normally is biased beyond cutoff. With the application of a one millisecond positive pulse from the modulation oscillator to the electronic switch 5, the grid of the tube |42 is raised to a less negative value so that the oscillations from the modulation oscillator are impressed upon capacitor |43 and are reproduced in the cathode circuit of the tube I 42 across a resistor |45. The output from the tube |26 is applied to the transmitter through the conductor I0. The approximate shapes of the pulses at the various stages in the circuit that is shown in Fig. 1, are shown below the capacitor |43, beside the resistor |45, above the capacitor |35 and above the resistor |40.

operatively, the transmitter is adapted to supply a radio carrier of, for example, the order of 100 mega-cycles, or the like. A single alternating-current pulse of the radio carrier is emitted by the transmitter over the transmitting antenna |2 with each depression of one of the switches 5 to 8 inclusive. Each radio carrier alternating-current pulse is, for example, of a time duration in the order of 100 microseconds 4 As referred to herein, an alternating-current pulse will be understood to mean a brief train of oscillations having a substantially rectangular wave envelope. Modulation of the radio carrier from the transmitter is accomplished by any, separately, or by any combination, concurrently, of the modulation oscillators to 4, inclusive, depending upon the closure of one or more of the corresponding modulation oscillator switches 5 to 8', inclusive, respectively.

The various frequencies of oscillation of the modulation oscillators to 4, inclusive, for purposes of convenient reference thereto, may be designated as the fixed frequency bands F1, F2, F3 and F4, respectively. For example, if the switch 5 of the electronic switch 5 is closed and the other modulation oscillator switches 6', 1 and 8 are open, then one alternating-current pulse of the radio carrier modulated to be within the frequency band F1 at which the modulation oscillator is oscillating, is radiated from the antenna 2. In a similar manner, if the switches 5' and 1 are closed, then the alternating-current carrier that is emitted during the brief interval of time that the transmitter is energized by electronic switches 5 and 1, is modulated simultaneously by oscillations within the frequency bands F1 and F3.

Each of the frequency bands F1, F2, F3 and F4 are, for example, of the order of 1 megacycle, or the like.

A preferred receiver circuit that is a part of the present invention is shown in block diagram in Fig. 2 of the accompanying drawings. In the receiver circuit shown, the alternating-current signal that is transmitted from the transmitter |0 over its transmitting antenna is intercepted by a receiver antenna 5 and is passed to and detected by a radio receiver I6. Amplified altermating-current output from the radio receiver 6 is applied to a desired plurality of filters |1, i8, I9, 2U, etc., that, for the purposes of the present explanation, may be assumed to correspond to the number of and to separately pass the modulation frequency bands F1, F2, F3, F4 etc. that are applied to the radio carrier by the modulation oscillators to 4, inclusive, respectively throughout. The modulating signals of the frequency bands F1, F2, F3, F4, etc. are recovered by detection in the radio receiver I6.

The alternating-current radio signals that are received and detected in the radio receiver i6 are amplied in usual manner in the broad band pass channel of the receiver I6 and the amplified alternating-current signals are then applied to the -bank of iilters |1 to 20, inclusive. Each iilter |1 to 20, inclusive, is selectively responsive to one of the detected modulated and amplied signal frequency bands F1, F2, F3 and F4, etc., respectively, and are passed through a corresponding number of rectiers 2|, 22, 23, 24 etc. as direct-current pulses to a corresponding number of electronic trigger circuits 25, 26, 2l, etc., and a trigger cancelling circuit 28, respectively, throughout. A direct-current pulse, Within the meaning of the presentspecication, is a discrete, unidirectional pulse as contrasted with a pulse made up of a train or packet of individual oscillations.

The direct-current pulses entering the trigger circuits 25 to 21, inclusive, or the trigger can.- celling circuit 28, appear as direct-current pulses of, in the example cited, l-microsecond time duration. Each of the trigger circuits 25 to 21, inclusive, provides positive direct-current pulses of continuing duration and the trigger cancelling circuit 28 provides .an elongated, self-terminating positive direct-current pulse. The direct-current pulses of continuing duration, as separate outputs of the trigger circuits 25, 26, and 21, are applied to relays 29, 3B and 3|, respectively, wherein the pulses energize individual relay windings to initiate the actuation of desired usual mechanisms in controls 32, 33 and 34, respectively, for the performance .of desired lmechanical, work thereby.

The positive direct-current self-terminating pulse output from the trigger cancelling circuit 23 is applied to the other trigger circuits 25, 2B and 21 for arresting the operation thereof. The direct-current pulse from the trigger cancelling circuit 28 is derived from an alternating-current modulating signal of the frequency F4 and the alternating-current pulse is lengthened out into a self-terminating positive direct-current pulse of longer time duration than the other alternating-current within the frequency bands Fi to Fa, inclusive.

The elongated signal terminating or cancelling positive direct-current pulse from the trigger cancelling circuit 23 serves both to deenergize the relay windings by terminating the direct-current pulses in the trigger circuits 2.5 to 21, inclusive, and to reset the trigger circuits 25 to 21, inclusive, for their next actuation upon the receipt of the next direct-current pulse that may be applied thereto. Upon the deenergization of the relay windings in the relays 29 to 3l, inclusive, operable elements of the corresponding controls 32 to 34, inclusive, respectively, are released automatically in any desired usual manner.

The absence of a continuous radio carrier and the brevity of the period oi transmission of the control signals in the frequency bands F1 to F4, inclusive, are advantageous in that they permit exceedingly high power to be concentrated into the signals at the transmitter. The high power of these `signals enables the signals to penetrate substantially any interfering radio carrier or signal oi lesser power and to be satisfactorily received therethrough at the receiver i6. As previously mentioned, the modulating frequency bands F1 to F4, inclusive, are of the order of l mega-cycle and the filters I1 to 20, inclusive, respectively, are tuned to the passing of these frequencies.

In operation, one or more alternating-current signals from the transmitter IB are intercepted by the receiving antenna l5 and are passed to the receiver i6. rEhe signals so received are amplied within the receiver I6 and the amplified signals are passed from the receiver to all of the iilters I1 to 2t, inclusive, in parallel. The lters l1 to inclusive, serve as band pass filters that channel the various alternating-current signals according to their respective frequencies F1 to F4, inclusive, and pass their respective alternating-current signals to the rectiers 2l to 24, inclusive, respectively, in which the signals are converted into direct-current signals. The resultant direct-current pulses are passed from the rectifiers. 2I to 24, inclusive, to their respective trigger circuits 25 to 21, inclusive, and the trigger cancelling circuit 2B. The direct-current pulses so applied to the trigger circuits 25 to 21, inclusive, are of continuous duration therein and cause current to flow through the corresponding relays 28 to 3l, inclusive, and continuously energize the relay windings thereof. The -energization of the windings of the relays 29 to v3l, inclusive, is effective to close the contacts thereof and apply current flow to the corresponding vcontrols L12 to 34, inclusive, that accomplish mechanical Work. The trigger cancelling circuit 28 passes a direct-current, seliterminating positive pulse of increased timeduration to all of the trigger circuits 25 to 2l', inclusive, and serves to terminate the direct-current flow of continuous duration therein and to reset the trigger circuits 25 to 21, inclusive, preparatory to the reception of additional alternating-current signals by the receiver I6. Upon the resultant deenergization .of the relay windings in the relays 29 to 3| inclusive, the operable elements of the controls 32 to 34, inclusive, respectively, are released.

A `block yand schematic diagram augmenting the showing in Fig. 2 is presented in Fig. 3 of the accompanying drawings. In the circuit that is shown in Fig. .3, alternating-current signals that are radiated by the transmitter II from its antenna I2 are intercepted by the receiving antenna I5 and are passed to the receiver I6 Where the received signals are amplied and impressed upon a. desiredplurality of the filters I1 to 2D, inclusive, that pass individually different illustrative frequency bands F1 to F4, inclusive, respectively. The iilters I1 to 20, inclusive, selectively pass alternating-current signals of frequency bands Fi to- F4, inclusive, into their respective channels and to a corresponding plurality of the grounded rectiers 2I to 24, inclusive, respectively, throughout. The direct-current pulse outputs of the rectiers 2l, 22 and 23 are passed respectively to a corresponding' plurality of the electronic trigger circuits 25, 26 and 21, respectively. The trigger circuits 25, 26 and 21 are substantially duplications of each other and hence the detailed circuitdescription of one trigger circuit may be taken as being illustrative of the description of the other two, all of which are .modiiications of the usual Eccles-Jordan multivibrator or flip-nop circuit.

A positive direct-current input pulse, as applied to an illustrative trigger circuit 25, is impressed `across a rectifier load resistor 4B to ground and through a blocking capacitor 4I to the grid of a triode electron tube 42. The grid of the tube 42 is cross-connected through a resistor 43 to the plate of another triode electro-n tube 44, the cathode of which is grounded through a resistor 45. The negative terminal of a suitable direct-current source, such as the battery 46 'or the like, that has its positive terminal connected to ground, provides bias supply to the grids of the tubes 42 and 44 through isolating resistors 41. and 48, remectively. The plate of the tube 42'is connected through a resistor 49 with the grid of the tube 44. Plate current from a suitable source of positive direct current, such as the B-I- source shown, is applied through isolating resistors 50 and 5I to the plates of the tubes 42 and 44, respectively. The cathode of the tube 42 is grounded through the Winding ofthe relay Z9. Upon the energization of the winding of the relay 29, its contact or switch is closed and circuit to the control -32 is completed. The trigger circuits 26 and 21 are duplications of the trigger circuit 25 in structure and in functions.

Receive-d 4alternating-current signals within the frequency band Fi, that are passed by the filter 20 and that are rectied as positive directcurrent pulses in the rectifier 24, are passed to the trigger cancelling circuit 28 in which the positive direct-current pulses are applied across a resistor 55 that is grounded at one end and that has its ungrounded end connected in parallel to the trigger circuits 25, 26 and 2T. A positive direct-current pulse across the resistor 55 is applied to the grid of the tube 44 through a blocking capacitor 56, and is similarly applied through corresponding blocking capacitors, not shown, in the trigger circuits 26 and 21.

In operation, alternating-current signals originating in one or more of the modulation oscillators I, 2, 3 or 4, depending upon which of the Switches 5', 6', I or 8' is closed, are emitted from the transmitter II through its transmitting antenna I2 and are intercepted by the receiving antenna I5 and passed to the receiver I6 in the receiving system. The .alternating-current output from the receiver I6 is applied to they filters IT, I8, I9 and 20 that channel the alternatingcurrent signals in conformity with the frequencies o'f the received signals. The filters I1, I8, I9 and 20 selectively pass alternating-current signals falling within their respective frequency bands F1, F2, F3 and F4, respectively.

Upon the reception of an alternating-current signal pulse of a. freqency that falls within the frequency band F1 signal is passed by the filter I'I and is converted from alternating to direct current in the rectifier 2 I The positive direct-current pulses which are derived from the alternating-current pulses that are fed into the rectifier 2| are passed thereby to the electronic trigger circuit 25. The time period of ea-ch input pulse and of each positive direct-current pulse preferably is predetermined, as, for example 100Y microseconds or the like.

A square wave pulse of positive direct-current electricity passed from the rectifier 2 I, to which the grounded load resistor 4D is applied, is effective to build up a positive potential on the blocking ca-pacitor 4I within the electronic trigger circuit 25. The positive potential pulse on the capacito-r 4I is applied to the grid of the tube 42 where it initiates a continuous current ow through the plate and cathode circuit of the tube 42 and simultaneously blocks the ow of current through the plate and cathode circuit of the tube 44. The flow of current through the grid and cathode circuit of the tube 42 passes to positive ground through and energizes the winding of the relay 29 and thereby closes the contact or switch of the relay 29 to complete the circuit through the control 32 for the doing of mechanical work.

The continuous flow of current through the plate and cathode circuit of the tube 42, that continues to draw current after the control alternating-current signal has ceased, is arrested at will by signal within the frequency band F4 originating in the modulation oscillator 4, shown in Fig. l., such signal passing through the switch 8 in its closed position to the transmitter II and being transmitted therefrom over the transmitting antenna I2. The alternating-current signal within the F4 band of frequencies is intercepted by the receiving antenna I5, shown in Fig. 3, amplified in the receiver I6 and is passed by the lter 20 to the rectier 24 as an alternating-current pulse. The alternating-current pulse is rectified `and lengthened in the rectifier 24 into a self-terminating pulse of positive direct-current and of longer time duration than any of the other alternating-current pulses in the frequency bands F1, F2 or F3 that are rectified and passed to the trigger circuits 25, 26 or 2'I, respectively. The

elongated, self-terminating, DOsitive direct-current pulse so produced is applied across the grounded resistor 55 and is applied simultaneously in parallel to all of the trigger circuits 25, 26 and 21.

In the period during which the contact or switch of the relay 29 is being held closed, the elongated, self-terminating pulse of positive direct-current voltage from the rectier 24 is applied through the blocking capacitor 56 to the grid of tube 44 in the trigger circuit 25'. The pulse so applied initiates current lflow between the plate and the cathode of the tube 44, which results in blocking the current flow between the plate and cathode of the tube 42, thus deenergizing the winding of the relay 29. The deenergization of the winding of the relay 29 permits its contact or Switch arm to open under spring tension in usual manner and interrupts the circuit through the control 32 land stops the mechanical work being done thereby.

The blocking of the current now between the plate and the cathode of the tube 42 resets the trigger circuit 25 for its actuation by the next alternating-current pulse signal within the frequency band F1 that is passed by the lter I'I. The reception of a cancelling alternating-current signal within the frequency band F4, that passes the filter 20 in the above described manner, cancels any and all alternating-current control signals that have previously been imposed upon any or all of the trigger circuits 25,y 26 and 2l in the manner described for the trigger circuit 25. Following the imposition of a cancelling signal within the frequency band F4 upon the trigger cancelling circuit 28, all of the trigger circuits 25, 26 and 2'! are reset for the imposition thereupon of further control signals that may be terminated subsequently by the imposition of a following cancelling signal upon the trigger cancelling circuit 28.

A representative schematic showing of the nlters I'I to 20, inclusive, as for example, filter Il, and of an electron tube type of the rectiers ZI to 24, inclusive, for example, rectier ZI is shown illustratively in Fig. 4 of the accompanying drawings. In the portion of the system circuit there shown, output from the receiver I6 in the form of an alternating-current sine wave, shown beneath the receiver I6, is applied across the primary winding 6I! of a transformer 6I that is disposed within the filter I'I. The primary winding 60 of the transformer 6I is tuned to the frequency band F1 in any desired manner, as by a tuning capacitor 62, or the like. The secondary winding 63 of the transformer 6I in the filter il is similarly tuned by a tuning capacitor 54. The output from the transformer 6I is applied across the plate and ground of a diode rectifier 65, within the rectifier 2I. The cathode of the tube 65 is grounded through a cathode resistor G6 shunted by a radio-frequency by-pass capacitor Si within the rectifier 2|. The positive direct-current pulse output from the cathode side of the tube 65 in the rectier 2I is applied directly from the cathode of the tube E5 to the trigger circuit 25 as a positive square wave pulse shown therebetween.

The alternating-current pulse output from the receiver I6 is, i-n the described manner, rectified and applied as a direct-current pulse to the trigger circuit 25, `and in parallel to the other trigger circuits 26 and 2 and tothe trigger cancelling circuit 28. Other types of rectiiiers, such as metallic oxide, crystal, or the like, rectiers with suitable conventional modifications in the vaccompanying portions of the circuit, if preferred, may be substituted for the electron tube 65 in the rectiner 2 I, without departing from thescope of the present invention.

The rectifiers 2| to 24, inclusive, in the above described receiver portion of the system circuit that is shown in Fig. 3, may be omitted, if preferred, by resorting to suitable grid leak detector action in the grid circuits of the tubes 42 and 44 through the proper selection of values for the grid leak resistors 41 and 48, for the capacitor 4I and for the direct-current supply 46'.

In the event that the number of trigger circuits 25, 26, 21, etc. is such that amplification of the direct-current pulse output from the trigger cancelling circuit 28 is desirable, an amplifier 19, that is shown in Fig. 5, for boosting the signal amplication by the receiver I6 may be inserted at a desired position in the receiver circuit, and preferably between the filter 20 and rectifier 24, as is shown in Fig. 5 of the drawing. In the receiver circuit portion there shown, the alternating-current output from the filter 20 is applied to the grid of an amplifier tube 1I that is disposed within the amplifier 10. A grid leak resistor 12 and a cathode resistor 13 that is shunted by a radio-frequency by-pass capacitor 14, are con'- nected to ground from the grid and cathode of the tube 1 I, respectively, so that the grid is maintained at a substantially fixed negative ground potential with respect to the cathode of the tube 1I and so that negative feedback is reduced. A suitable positive direct-current source, such as B-I- shown, or the like, supplies direct-current plate current through a choke coil 15 or the like, to the plate of the tube 1I from which an amplified alternating-current output is passed from the amplifier l0 to the rectifier 24 for rectification therein.

A modification of the receiving portion of the system circuit is shown in Fig. 6 of the accompanying drawings. In this modification of the receiver circuit the trigger actuating and trigger cancelling circuit signals are negative-going pulses of direct-current whereas the comparable signals in the receiver circuit that is shown in Fig. 3 are pulses of positive direct current.

In the receiver portion. of the system circuit that is shown in Fig. 6 of the drawings, alternating-current signal pulses that originate in any of the modulation oscillators I to 4, inclusive, shown in Fig. 1, and that are transmittedy by the transmitter Il, are intercepted by a receiving antenna 89 and are passed to the receiver 8| and provide signal input to the receiving portion of the system circuit. The alternating-current signals so received are of predetermined groups of frequencies that are distinguished from each other, as by being within the frequency bands Fi, F2, F3 and F4 to which a desired plurality of filters 82, 83, 84 and 85, respectively, are tuned.

The alternating-current pulse output from the receiver 9| is applied in parallel to the filters 62 to 69, inclusive. The filters 82 to 85, inclusive, channel the received alternating-current pulses depending upon their frequencies and pass them to a corresponding plurality of rectiers 86, 81, 88 and 89, respectively. Each of the filters 82 to 35, inclusive, comprises a tuned transformer, such as the transformer 6I of the lter I1 that is shown in Fig. 4. The outputs from each secondary winding of the transformers in the filters 82 to 85, inclusive, are applied to the rectifiers 86 to 89, inclusive, respectively.

The rectifiers 86 to 89, inclusive, are duplications of each otherA and the description-ofv the schematic circuit diagram for the rectifier 86, that is vshown in Fig. 6, may be taken as beingV representative of the other rectifiers 81, 88 and 99 therein. The output from the secondary Winding of the transformer in the filter 82 is applied across the plate and directly grounded cathode of a rectifier tube 90 in the rectifier 86. A cathode resistor and radio-frequency by-pass combination 9i is inv series between the cathode side of the.

secondary winding of the transformer in the filter 82 and the directly grounded cathode of the tube 90. The output from the rectifier 86 is a negative direct-current pulse and is taken directly from the cathodeside of the secondary winding of the transformer within the filter 82 and is applied through ablocking capacitor 95 to the cathode of a triode electron tube 96 within a trigger circuit 91.

Outputs from the plurality of rectiers 86,` 81 and 88 are applied to a corresponding plurality of trigger circuits 91, 98 and 99'. The output from the rectifier 89 is an elongated, negative, selfterminating direct-current pulse and is applied in parallel to the triggerv circuits` 91, 98 and 99 for cancelling the current flow therein and resetting the trigger circuits 91, 98 and 99 for the reception of other signals. The circuits of the trigger circuits 91, 98 and 99 are duplications of each other and the description of the circuit of Y the trigger Vcircuit 91 may be taken as being illustrative of theA circuits of the other trigger circuits 98 and 99.

The application of the negative pulse fromV the rectifier 86 through the blocking capacitor 95 to the cathode of the 'electron tube 96 momentarily throws cathode of the tube 96 more negative than ground potential and sufficiently negative with respect to the grid of the tube 99 so that the tube 96 conducts to ground through the winding of a relay 92. The energization of the winding of the relay 92 closes the contact or switch of the relay 92 and closes the circuit of a control 93 thereby causing mechanical work to be performed. This flow of current through the winding of the relay 92 continues as long as current from the plate of the tube 96 continues to flow to the cathode of the tube 96 and through the, winding of the relay 92 to ground, Positive direct-current is supplied to the plate of the tube 96 and to the plate of another tube 99 within the trigger circuit 91 through isolating resistors |00 and I9-| respectively, from a suitable source, such as'from the B+ current source shown, or the like. Y

The plate of the tube 96 is connected through a resistor |02 with the grid of the tube 99. `The plate of the tube 99 is connected through a resistor |03 with the grid of the tube 96. A negative direct-current potential from a suitable source, such' as a battery |04, that has its positive terminal connected to ground, or the like, is applied through resistors |05 and |06 to the grids of the tubes 96 and 99', respectively.

yThe contact or switch of the relay 92 continues to be closed until an alternating-current signal of a frequency within the frequency band F4 and originating within the modulation oscillator 4, is broadcast from the transmitting antenna I2 upon the depression of the sending key 6' and is intercepted by the receiving antenna and applied by the receiver 8| to the filter B5. The alternating-current signal wit-hin the frequency band F4. is passed by the filter and is converted by the rectifier 89 into an elongated, self-terminating, negative, direct-current pulse inthe same manner in which the rectifier 86 operates upon a corresponding signal of F1 that is passed by the lter 82. The resultant negative pulse is applied in parallel to the trigger circuits 9'I, 98 and 99 and functions therein as in the representative trigger circuit 91.

The negative pulse from the rectifier 89 and applied to the trigger circuit 91 is applied to ground through a resistor I 01 therein and is applied through a blocking capacitor IIO directly to the cathode of the tube 99'. The cathode of tube 99 is applied to ground through a choke coil I I I. The application of the negative pulse to the cathode of the tube 99 drives it more negative than the grid of the tube 99 and causes the tube 99 to conduct. The flow of current from the plate to the cathode of the tube 99 also makes the grid of the tube 96 less positive by reason of the voltage drop through the resistor |03 and arrests the flow of current through the tube 96. Stopping the current flow through the tube 96 deenergizes the winding of the relay 92 and permits the contact or switch of the relay 92 to open under spring tension in the usual manner. The opening of the contact or switch of the relay 92 interrupts the circuit in the control 93 and arrests the mechanical work being done therein. The self-terminatingr characteristic of the negative pulse from the rectifier 89 quenches the current flow in the tube 96 and restores it to its quiescent condition preparatory to the reception of the next control signal. The trigger circuit 98 operates a relay I I5 and control I I 6 and the trigger circuit 99 operates the relay II'I and the control II8 in the same manner in which the trigger circuit 9'I operates its relay 92 and control 93.

It is to be understood that the circuits, the components in the circuits and the arrangements thereof, that have been disclosed and described herein have been submitted for the purposes of illustrating and describing suitable embodiments of the present invention and that similarly operating modications, substitutions and rearrangements thereof may be made without departing from the present invention.

What we claim. is:

1. A remote control system including: transmitter means for generating a radio carrier; a plurality of modulating oscillators of different frequencies; an equal plurality of multivibrators respectively coupled between said plurality of oscillators and said transmitter means for respectively pulsing the output of each of said oscillators as well as said transmitter means; an equal plurality of means respectively coupled to and triggering said plurality of multivibrators; receiver means for receiving and demodulating the modulated radio carrier pulses sent out by said transmitter means; an equal plurality of fllter means, corresponding respectively to said plurality of modulating oscillators, coupled to the output of said receiver means, each of said lter means being respectively pretuned to the corresponding frequency of its respective modulating oscillator; and an equal plurality of energy translating means, each coupled respectively to said plurality of lter means and adapted to be activated by the output therefrom.

2. A remote control system including: transmitter means for generating a radio carrier; a plurality of modulating oscillators of diierent frequencies; an equal plurality of means coupled between said oscillators and said transmitter means for respectively pulsing the output of each of said oscillators as well as said .transmitter means; receiver means for receiving and demodulating the modulated radio carrier pulses sent out by said transmitter means; an equal plurality of filter means, corresponding respectively to said plurality of oscillators, coupled to the output of said receiver means, each of said filter means being respectively pretuned to the corresponding frequency of its respective oscillator; an equal plurality of single kick multivibrator circuits respectively coupled to and adapted to be activated by the outputs from said filter means; and an equal plurality of energy translating means, each coupled respectively to said plurality of multivibrator circuits and adapted to be activated by the output therefrom.

3. A system according to claim 2, further including an additional, different frequency, modulating oscillator; an additional pulsing means coupled between said 4additional oscillator and said transmitter means for pulsing said transmitter means and said additional oscillator; additional lilter means coupled to the output of said receiver means and pretuned to said additional frequency; and a cancelling circuit coupled between the output from said additional lter means and said plurality of multivibrator circuits, whereby said multivibrator circuits may be deactivated and restored to a non-conductive state thereby ceasing to activate said translating means.

4. In a remote control system, a receiver for receiving and demodulating radio carrier pulses sent out by a transmitter; a plurality of lter means coupled to the output of said receiver, each of said lter means being pretuned to a different one of and equal plurality of modulation frequency imposed upon said carrier pulses, for respectively channeling each modulation frequency; an equal plurality of single kick multivibrator circuits respectively coupled to and adapted to be activated by the respective outputs from said plurality of iilter means; and an equal plurality of energy translating means respectively coupled to the outputs of said plurality of multivibrator circuits and adapted to be activated thereby.

5. A receiver according to claim 4, further including an additional lter means coupled to the output of said receiver and pretuned to an additional modulation frequency imposed upon said carrier pulses at said transmitter; and a cancelling circuit coupled between the output from said additional lter means and each of said plurality of multivibrator circuits, whereby said multivibrator circuits may be deactivated and restored to a non-conductive state thereby ceasing to activate said translating means.

6. A receiver according to claim 5, wherein said cancelling circuit comprises an impedance load for the output from said additional filter means.

7. In a remote control system, a transmitter including: means for generating a radio carrier wave; at least one source of modulation waves; a multivibrator coupled between said source of modulation waves and said transmitter means for pulsing the output of said source of modulating waves as well as said generating means; and means coupled to and triggering said multivibrator.

8. A transmitter according to claim 7, further including normally inoperative switch means coupled to and adapted to be activated by the output from said multivibrator, the output of said source of modulation wavestteing coupled to the input of said switch means, the output of said switch mea-ns being coupled to the input of said generator means.

THEODORE M. IVIANLEY. ROBERT P. CHERPESKI.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date Webbe Nov. 80, 1926 Number 14 Name Date Hammond, Jr Aug. 11, 1931 Luck Mar. 18, 1941 Reeves Feb. 3, 1942 Tuniek May 5, 1942 Clay Mar. 26, 1946 Luck Mar. 18, 1941 Crosby Aug. 17, 1948 .Starr Mar. 14, 1950 Hammond May 23, 1951 Murray et a1. Jan. l, 1952 

